Hi Mauro, basically with the "fill in patch by patch" strategy it's a dying art form even in programs with multi-sided G2 continuity blending because it's so sensitive. Just having G2 continuity by itself doesn't do enough, even if a surface is G2 to another right at an edge, if the surface curvature changes too much in a localized area around the boundary it will leave some visible evidence of the patch topology in the model.

The other thing that happens is corners can be difficult, it's easy for the blend to have competition between different shapes right in corner areas. It's also difficult to make shaping adjustments with it.

It takes a great amount of experience to deal with these problems, so it's a very high learning curve type of modeling strategy.

In general it's a strategy that has been dropped by most people doing complex surfacing in favor of Sub-d modeling. It's a trend that has been going on for a long time, sub-d modeling was actually invented as an easier to use organic surface modeling strategy specifically because doing character models with NURBS patch by patch modeling is so difficult. "Geri's Game" back in 1997 was the big turning point for this in the "DCC" / animation-oriented modeling world.

So it's not an area that I'm particularly excited to put a lot of effort into. It can be useful in limited circumstances but it's not really a winning primary modeling strategy for complex surfaces.

You get better quality for things that are supposed to be smooth by making larger extended surfaces that get cut back rather than trying to fill things in patch by patch. If it's difficult to make out of one larger surface then Sub-d is better, it's more predictable and controllable. It has a learning curve too though, higher than 2D profile driven NURBS modeling but not as high as patch-by-patch surfacing type NURBS modeling.

2D profile driven NURBS modeling has one of the lowest learning curves so it's generally been an area I've been more focused on.

The Sub-d modeling method is a possible workflow now in MoI v4 with the converter which is currently the highest quality converter available. You construct your sub-d control cage in a sub-d modeler, not in Moi but it generally makes more sense for me to work on introducing sub-d modeling methods in MoI for advanced surfacing rather than patch-by-patch NURBS surfacing methods.

If I am able to, I would like to have more types of NURBS continuity tools in MoI too though, they can be useful it's just not a high priority because of all that I described above.

- Michael